The present invention relates generally to an automotive airbag and a folding method and system thereof. More particularly, the present invention relates to a so-called curtain airbag which deploys along the side windows of the vehicle upon collision, and a folding method and system thereof.
In the field of airbags which expand and deploy by introduction of gas, the so-called curtain airbag is known which deploys along the side windows of the vehicle upon collision. Ordinarily, the curtain airbag is folded in narrow shape and disposed along a roof side rail of the vehicle. And when the vehicle undergoes an impact from the side, the airbag has gas introduced therein to expand and deploy downward along the windows.
U.S. Pat. No. 6,371,512 B1 discloses an automotive curtain airbag folded in narrow shape and disposed along a roof side rail of the vehicle, wherein the airbag is constructed flat on the side of the roof side rail, and is folded like a bellows on the side of a head lining or a seat occupant. As being folded in narrow shape and disposed along the roof side rail of the vehicle, the curtain airbag is required to allow smooth introduction of gas from one end to another end and deploy stably along the windows. Moreover, the curtain airbag is larger in longitudinal dimension or length than the airbag provided to the steering wheel, so that its fully manual folding raises a problem of taking much work time.
PCT Application WO 99/20492 discloses a system for automatically folding a curtain airbag, which comprises two rolls each provided with a plurality of ridges protruding circumferentially. The rolls are combined to have the ridges engaged with each other for rotation. Then, an unfolded airbag is fed to a space between the rolls along the length direction, obtaining the airbag folded like a bellows (fanfold airbag).
The structure of feeding an airbag to a space between the rolls may be suitable for folding of an airbag at a predetermined small depth and like a bellows, which, however, often provides tension to a cloth along the width direction during folding. Thus, folding work is not always easy when folding an airbag in deep undulations or in undulations having shallow and deep portions. Specifically, during folding, an airbag as extended flat is narrowed in the width direction or in the height direction upon deployment, providing tension to the cloth along the height direction. Then, if a portion with one undulation is folded deeply, a shallow portion adjacent to the deeply folded portion also undergoes great tension.
When arranging in the airbag an inner pipe or gas lance which serves as a passage for receiving gas first and guiding it to other parts, it is important for deployment of the airbag in a desired state to stably fold a portion with inner pipe in a predetermined shape. However, the inner pipe is disposed in the length direction of the airbag and along one end in the width direction thereof, so that even if the portion with inner pipe is restrained for positioning, the airbag is deformed by being pulled to the center in the width direction in the folding process, leading to difficult achievement of desired constant folded undulations. Folding the airbag in a desired shape needs an enhancement in strength of the airbag or complicated control means for restraining tension to be applied to the airbag, for example. Then, if the reinforcement of a cloth or the use of a cloth of greater weight is carried out to enhance the strength of the airbag, it becomes difficult to fold the airbag in a small size, which creates a undesirableness for a curtain airbag to which small-size folding capability is demanded. On the other hand, the control means for restraining tension to be applied to the airbag brings complication of the device, resulting in difficult restraint of manufacturing cost. Particularly, a cloth which allows compact accommodation lacks flexibility, and thus tends to cause hard positioning in the folding process, requiring highly developed means, raising a problem of difficult restraint of manufacturing cost.